594 On the EleSfrtcity excited hy the 



the temperature of the ambient air, or that of the water or 

 moiftened difks which enter into the compofition of the co- 

 lumn, and that of the water even in the bafon, is warmer, 

 as heat renders the water a better condu6lor. But almoft all 

 the falls, and particularly common fait, will render it a ftill 

 better. This is one of the reafons, if not the only one, why 

 it is fo advantageous that the water of the bafon, and, above 

 all, that interpofed between each pair of metallic plates, as 

 well as the water with which the circular pieces of pafteboard 

 are impregnated, &c. fliould be fait water, as already ob- 

 ferved. 



But all thefe means and all thefe attentions have only a 

 limited advantage, and will never occafion your receiving 

 very ftrong ftiocks as long as the apparatus confifts but of 

 one column, formed only of twenty pair of plates, even 

 though they may confill of the two metals propereft for 

 thefe experiments, viz, filver and zinc ; for if they were 

 filver and lead, or tin, or copper and tin, the half of the 

 efledl would not be produced, unlefs the weaker effcft of 

 each pair were fupplied by a much greater number. What 

 teaJly increafes the ele<3:ric power of this apparatus, and to 

 fuch a degree as to make it equal or furpafs that of the torr 

 pedo or eleftric eel, is the number of plates arranged in fuch 

 a manner, and with the attention before meritioned. If to 

 the twenty pairs above delcribed twenty or thirty others be 

 added difpofe<l in the fame order, the Ihocks which may be 

 communicated by a column lengthened in this manner will 

 be much ftronger, and extend to both arms as far as the 

 flinulder; and el'pecially of that, the hand of which has been 

 inmierfed in the water : this hand, with the whole arm, will 

 remain more or lefs benumbed, if by frequently renewing 

 the touches thefe (lux-ks be made to fuccecd each other ra- 

 pidly, and without interniidion. This will be the cafe if 

 the whole hand, or the greater part of it, be inmierfed in the 

 water of the bafon ; but if only one finger be immerfed, either 

 ■wholly or in part, the fhocks being almoft entirely concen- 

 trated in it alone, will become fo much the more painful, 

 fnd fo acute a ; to be fcarcely fupportable. 



It may readily be conceived that this column, formed of 



forty 



